a) all phones will be smartphones (unlocked smartphones currently cost as little as $50 in China)

b) quality tablets will be incredibly cheap (less than $100). The Chinese are already selling unlocked 10" tablets with capacitative touchscreens for $200. That price will drop to $150 within a matter of months,

C) per unit profit margins will be tiny ($5-10).

So how is Apple going to mega profitable when they are hundreds of much cheaper products competing covering every single market segment?

This is how the PC almost killed Apple back in the mid 1990s.

Smartphones for $50 and tablets for €200 ?
Don't think so...
You do realise that the push is to make these devices as powerful as possible. Better screen, better cpu, more ram, better battery life, better camera. Add it up and that means that they're not going to approach $200 anytime soon, not the ones that are selling's in big numbers anyways.

Take a look at the music player market evolved these past 10 years and you'll get the idea.